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模块:Json2
-- JSON4Lua: JSON encoding / decoding support for the Lua language. -- json Module. -- Author: Craig Mason-Jones -- Homepage: http://github.com/craigmj/json4lua/ -- Version: 1.0.0 -- This module is released under the MIT License (MIT). -- Please see LICENCE.txt for details. -- -- USAGE: -- This module exposes two functions: -- json.encode(o) -- Returns the table / string / boolean / number / nil / json.null value as a JSON-encoded string. -- json.decode(json_string) -- Returns a Lua object populated with the data encoded in the JSON string json_string. -- -- REQUIREMENTS: -- compat-5.1 if using Lua 5.0 -- -- CHANGELOG -- 0.9.20 Introduction of local Lua functions for private functions (removed _ function prefix). -- Fixed Lua 5.1 compatibility issues. -- Introduced json.null to have null values in associative arrays. -- json.encode() performance improvement (more than 50%) through table.concat rather than .. -- Introduced decode ability to ignore /**/ comments in the JSON string. -- 0.9.10 Fix to array encoding / decoding to correctly manage nil/null values in arrays. ----------------------------------------------------------------------------- ----------------------------------------------------------------------------- -- Imports and dependencies ----------------------------------------------------------------------------- local math = require('math') local string = require("string") local table = require("table") ----------------------------------------------------------------------------- -- Module declaration ----------------------------------------------------------------------------- local json = {} -- Public namespace local json_private = {} -- Private namespace -- Public constants json.EMPTY_ARRAY={} json.EMPTY_OBJECT={} -- Public functions -- Private functions local decode_scanArray local decode_scanComment local decode_scanConstant local decode_scanNumber local decode_scanObject local decode_scanString local decode_scanWhitespace local encodeString local isArray local isEncodable ----------------------------------------------------------------------------- -- PUBLIC FUNCTIONS ----------------------------------------------------------------------------- --- Encodes an arbitrary Lua object / variable. -- @param v The Lua object / variable to be JSON encoded. -- @return String containing the JSON encoding in internal Lua string format (i.e. not unicode) function json.encode (v) -- Handle nil values if v nil then return "null" end local vtype = type(v) -- Handle strings if vtype 'string' then return '"' .. json_private.encodeString(v) .. '"' -- Need to handle encoding in string end -- Handle booleans if vtype 'number' or vtype 'boolean' then return tostring(v) end -- Handle tables if vtype 'table' then local rval = {} -- Consider arrays separately local bArray, maxCount = isArray(v) if bArray then for i = 1,maxCount do table.insert(rval, json.encode(vi)) end else -- An object, not an array for i,j in pairs(v) do if isEncodable(i) and isEncodable(j) then table.insert(rval, '"' .. json_private.encodeString(i) .. '":' .. json.encode(j)) end end end if bArray then return '.. table.concat(rval,',') ..'' else return '{' .. table.concat(rval,',') .. '}' end end -- Handle null values if vtype 'function' and v json.null then return 'null' end assert(false,'encode attempt to encode unsupported type ' .. vtype .. ':' .. tostring(v)) end --- Decodes a JSON string and returns the decoded value as a Lua data structure / value. -- @param s The string to scan. -- @param startPos Optional starting position where the JSON string is located. Defaults to 1. -- @param Lua object, number The object that was scanned, as a Lua table / string / number / boolean or nil, -- and the position of the first character after -- the scanned JSON object. function json.decode(s, startPos) startPos = startPos and startPos or 1 startPos = decode_scanWhitespace(s,startPos) assert(startPos<=string.len(s), 'Unterminated JSON encoded object found at position in .. s .. '') local curChar = string.sub(s,startPos,startPos) -- Object if curChar '{' then return decode_scanObject(s,startPos) end -- Array if curChar 'then return decode_scanArray(s,startPos) end -- Number if string.find("+-0123456789.e", curChar, 1, true) then return decode_scanNumber(s,startPos) end -- String if curChar [["] or curChar ' then return decode_scanString(s,startPos) end if string.sub(s,startPos,startPos+1) '/*' then return json.decode(s, decode_scanComment(s,startPos)) end -- Otherwise, it must be a constant return decode_scanConstant(s,startPos) end --- The null function allows one to specify a null value in an associative array (which is otherwise -- discarded if you set the value with 'nil' in Lua. Simply set t = { first=json.null } function json.null() return json.null -- so json.null() will also return null ;-) end ----------------------------------------------------------------------------- -- Internal, PRIVATE functions. -- Following a Python-like convention, I have prefixed all these 'PRIVATE' -- functions with an underscore. ----------------------------------------------------------------------------- --- Scans an array from JSON into a Lua object -- startPos begins at the start of the array. -- Returns the array and the next starting position -- @param s The string being scanned. -- @param startPos The starting position for the scan. -- @return table, int The scanned array as a table, and the position of the next character to scan. function decode_scanArray(s,startPos) local array = {} -- The return value local stringLen = string.len(s) assert(string.sub(s,startPos,startPos) 'called but array does not start at position ' .. startPos .. ' in string:\n'..s ) startPos = startPos + 1 -- Infinite loop for array elements local index = 1 repeat startPos = decode_scanWhitespace(s,startPos) assert(startPos<=stringLen,'JSON String ended unexpectedly scanning array.') local curChar = string.sub(s,startPos,startPos) if (curChar '') then return array, startPos+1 end if (curChar ',') then startPos = decode_scanWhitespace(s,startPos+1) end assert(startPos<=stringLen, 'JSON String ended unexpectedly scanning array.') object, startPos = json.decode(s,startPos) arrayindex = object index = index + 1 until false end --- Scans a comment and discards the comment. -- Returns the position of the next character following the comment. -- @param string s The JSON string to scan. -- @param int startPos The starting position of the comment function decode_scanComment(s, startPos) assert( string.sub(s,startPos,startPos+1) '/*', "decode_scanComment called but comment does not start at position " .. startPos) local endPos = string.find(s,'*/',startPos+2) assert(endPos~=nil, "Unterminated comment in string at " .. startPos) return endPos+2 end --- Scans for given constants: true, false or null -- Returns the appropriate Lua type, and the position of the next character to read. -- @param s The string being scanned. -- @param startPos The position in the string at which to start scanning. -- @return object, int The object (true, false or nil) and the position at which the next character should be -- scanned. function decode_scanConstant(s, startPos) local consts = { "true" = true, "false" = false, "null" = nil } local constNames = {"true","false","null"} for i,k in pairs(constNames) do if string.sub(s,startPos, startPos + string.len(k) -1 ) k then return constsk, startPos + string.len(k) end end assert(nil, 'Failed to scan constant from string ' .. s .. ' at starting position ' .. startPos) end --- Scans a number from the JSON encoded string. -- (in fact, also is able to scan numeric +- eqns, which is not -- in the JSON spec.) -- Returns the number, and the position of the next character -- after the number. -- @param s The string being scanned. -- @param startPos The position at which to start scanning. -- @return number, int The extracted number and the position of the next character to scan. function decode_scanNumber(s,startPos) local endPos = startPos+1 local stringLen = string.len(s) local acceptableChars = "+-0123456789.e" while (string.find(acceptableChars, string.sub(s,endPos,endPos), 1, true) and endPos<=stringLen ) do endPos = endPos + 1 end local stringValue = 'return ' .. string.sub(s,startPos, endPos-1) local stringEval = load(stringValue) assert(stringEval, 'Failed to scan number [ ' .. stringValue .. '] in JSON string at position ' .. startPos .. ' : ' .. endPos) return stringEval(), endPos end --- Scans a JSON object into a Lua object. -- startPos begins at the start of the object. -- Returns the object and the next starting position. -- @param s The string being scanned. -- @param startPos The starting position of the scan. -- @return table, int The scanned object as a table and the position of the next character to scan. function decode_scanObject(s,startPos) local object = {} local stringLen = string.len(s) local key, value assert(string.sub(s,startPos,startPos) '{','decode_scanObject called but object does not start at position ' .. startPos .. ' in string:\n' .. s) startPos = startPos + 1 repeat startPos = decode_scanWhitespace(s,startPos) assert(startPos<=stringLen, 'JSON string ended unexpectedly while scanning object.') local curChar = string.sub(s,startPos,startPos) if (curChar '}') then return object,startPos+1 end if (curChar ',') then startPos = decode_scanWhitespace(s,startPos+1) end assert(startPos<=stringLen, 'JSON string ended unexpectedly scanning object.') -- Scan the key key, startPos = json.decode(s,startPos) assert(startPos<=stringLen, 'JSON string ended unexpectedly searching for value of key ' .. key) startPos = decode_scanWhitespace(s,startPos) assert(startPos<=stringLen, 'JSON string ended unexpectedly searching for value of key ' .. key) assert(string.sub(s,startPos,startPos) ':','JSON object key-value assignment mal-formed at ' .. startPos) startPos = decode_scanWhitespace(s,startPos+1) assert(startPos<=stringLen, 'JSON string ended unexpectedly searching for value of key ' .. key) value, startPos = json.decode(s,startPos) objectkey=value until false -- infinite loop while key-value pairs are found end -- START SoniEx2 -- Initialize some things used by decode_scanString -- You know, for efficiency local escapeSequences = { "\\t" = "\t", "\\f" = "\f", "\\r" = "\r", "\\n" = "\n", "\\b" = "\b" } setmetatable(escapeSequences, {__index = function(t,k) -- skip "\" aka strip escape return string.sub(k,2) end}) -- END SoniEx2 --- Scans a JSON string from the opening inverted comma or single quote to the -- end of the string. -- Returns the string extracted as a Lua string, -- and the position of the next non-string character -- (after the closing inverted comma or single quote). -- @param s The string being scanned. -- @param startPos The starting position of the scan. -- @return string, int The extracted string as a Lua string, and the next character to parse. function decode_scanString(s,startPos) assert(startPos, 'decode_scanString(..) called without start position') local startChar = string.sub(s,startPos,startPos) -- START SoniEx2 -- PS: I don't think single quotes are valid JSON assert(startChar " or startChar ','decode_scanString called for a non-string') --assert(startPos, "String decoding failed: missing closing " .. startChar .. " for string at position " .. oldStart) local t = {} local i,j = startPos,startPos while string.find(s, startChar, j+1) ~= j+1 do local oldj = j i,j = string.find(s, "\\.", j+1) local x,y = string.find(s, startChar, oldj+1) if not i or x < i then i,j = x,y-1 end table.insert(t, string.sub(s, oldj+1, i-1)) if string.sub(s, i, j) "\\u" then local a = string.sub(s,j+1,j+4) j = j + 4 local n = tonumber(a, 16) assert(n, "String decoding failed: bad Unicode escape " .. a .. " at position " .. i .. " : " .. j) -- math.floor(x/2^y) lazy right shift -- a % 2^b bitwise_and(a, (2^b)-1) -- 64 = 2^6 -- 4096 = 2^12 (or 2^6 * 2^6) local x if n < 0x80 then x = string.char(n % 0x80) elseif n < 0x800 then -- xxxx xxxx x = string.char(0xC0 + (math.floor(n/64) % 0x20), 0x80 + (n % 0x40)) else -- xxxx xxxx xxxx x = string.char(0xE0 + (math.floor(n/4096) % 0x10), 0x80 + (math.floor(n/64) % 0x40), 0x80 + (n % 0x40)) end table.insert(t, x) else table.insert(t, escapeSequencesi, j)) end end table.insert(t,string.sub(j, j+1)) assert(string.find(s, startChar, j+1), "String decoding failed: missing closing " .. startChar .. " at position " .. j .. "(for string at position " .. startPos .. ")") return table.concat(t,""), j+2 -- END SoniEx2 end --- Scans a JSON string skipping all whitespace from the current start position. -- Returns the position of the first non-whitespace character, or nil if the whole end of string is reached. -- @param s The string being scanned -- @param startPos The starting position where we should begin removing whitespace. -- @return int The first position where non-whitespace was encountered, or string.len(s)+1 if the end of string -- was reached. function decode_scanWhitespace(s,startPos) local whitespace=" \n\r\t" local stringLen = string.len(s) while ( string.find(whitespace, string.sub(s,startPos,startPos), 1, true) and startPos <= stringLen) do startPos = startPos + 1 end return startPos end --- Encodes a string to be JSON-compatible. -- This just involves back-quoting inverted commas, back-quotes and newlines, I think ;-) -- @param s The string to return as a JSON encoded (i.e. backquoted string) -- @return The string appropriately escaped. local escapeList = { '"' = '\\"', '\\' = '\\\\', '/' = '\\/', '\b' = '\\b', '\f' = '\\f', '\n' = '\\n', '\r' = '\\r', '\t' = '\\t' } function json_private.encodeString(s) local s = tostring(s) return s:gsub(".", function© return escapeListc end) -- SoniEx2: 5.0 compat end -- Determines whether the given Lua type is an array or a table / dictionary. -- We consider any table an array if it has indexes 1..n for its n items, and no -- other data in the table. -- I think this method is currently a little 'flaky', but can't think of a good way around it yet... -- @param t The table to evaluate as an array -- @return boolean, number True if the table can be represented as an array, false otherwise. If true, -- the second returned value is the maximum -- number of indexed elements in the array. function isArray(t) -- Next we count all the elements, ensuring that any non-indexed elements are not-encodable -- (with the possible exception of 'n') if (t json.EMPTY_ARRAY) then return true, 0 end if (t json.EMPTY_OBJECT) then return false end local maxIndex = 0 for k,v in pairs(t) do if (type(k) 'number' and math.floor(k) k and 1<=k) then -- k,v is an indexed pair if (not isEncodable(v)) then return false end -- All array elements must be encodable maxIndex = math.max(maxIndex,k) else if (k 'n') then if v ~= (t.n or #t) then return false end -- False if n does not hold the number of elements else -- Else of (k 'n') if isEncodable(v) then return false end end -- End of (k~='n') end -- End of k,v not an indexed pair end -- End of loop across all pairs return true, maxIndex end --- Determines whether the given Lua object / table / variable can be JSON encoded. The only -- types that are JSON encodable are: string, boolean, number, nil, table and json.null. -- In this implementation, all other types are ignored. -- @param o The object to examine. -- @return boolean True if the object should be JSON encoded, false if it should be ignored. function isEncodable(o) local t = type(o) return (t 'string' or t 'boolean' or t 'number' or t 'nil' or t 'table') or (t 'function' and o json.null) end return json